A common cause for an automobile alternator to cease charging is a defective voltage regulator. Very frequently if there is no charging, then the alternator is replaced, and when the alternator is torn down, it is found to be not defective. In some cases it has been found that solid state replacement regulators in stock are also defective. However, discovery of this is not made until after installation of the new alternator, such replacing of alternators having been unnecessary in the first place. Discovery of the defective solid state regulators has been due to the fact that the conventional testing methods with existing apparatus has been quite time consuming. Therefore, usually no attempt is made to verify the working condition of the solid state device prior to installation. Also, when Ford and General Motors inspectors visit dealers for the purpose of checking warranty parts they are unable to verify the state of the solid state voltage regulator, again due to the time consuming process now required for testing. The simplified test will enable rapid testing of the entire stock to ensure reliable and dependable replacement parts, saving the dealer and consumer time and costs.